Tooth root canal treatment is usually made by hand by the dentist holding the rear end of a tooth root canal file between his forefinger and thumb and slightly rotating it to and fro while inserting it into the tooth and moving it down through the canal. However, there are also previously known automatically driven systems for treatment of the tooth root canals, but very few of them have been put on the market.
A previously known automatically driven system is discussed in U.S. Pat. No. 4,629,426 by Levy. The endodontic treatment instrument described by Levy includes a tooth root canal file inserted in a driving means, which vibrates the file in its axial direction while rotating it to and fro. The amplitude of the vibrations is maximum when the file does not meet any resistance and is reduced to a small value upon encountering an obstacle.
A disadvantage with this prior endodontic treatment instrument is that it is difficult to point the tip of the file exactly right into the opening in the tooth at insertion because of its vibration at maximum amplitude at that moment. It is also a disadvantage to have the minimum vibration amplitude just at an obstacle to get past.
It is an object of the present invention to provide a dental instrument, which does not vibrate when unloaded, i.e. when no part of it is placed in a tooth. In this way it will be easy to steer the tip of the instrument tool, such as a tooth file, exactly into a tooth root canal in a tooth.
It is another object of the invention to provide a dental instrument in which the instrument tool, such as a file, begins to rotate and vibrate as soon as it meets a resistance in axial direction.
It is a further object of the present invention to provide a dental instrument having its maximum vibration amplitude when meeting an obstacle in order to facilitate passage of the instrument tool.
These and other objects of the subject invention will become apparent from the description which follows and by reference to the attached drawings.
The invention is based upon a prior instrument described in the U.S. Pat. No. 3,552,022 owned by the same applicant. Changes have been made in this instrument in order to have the features aimed at above in order to make the inventive instrument.